Seismic borehole plug

ABSTRACT

A tubular inflatable bag has its lower end secured to a bottom closure cap at the lower end of an air pipe which has a lateral passage for admitting air under pressure into the bag. The upper end of the bag is secured to a top closure cap which is slidable along the pipe as the bag expands during inflation. Upward sliding of the top cap is limited by an abutment provided on the pipe above the bag, the abutment consisting of a housing which contains a valve for controlling airflow through the pipe.

United States Patent References Cited UNITED STATES PATENTS 2,079,830 5/1937 Baker et a] 166/187 2,618,344 11/1952 Turechek etal 166/187 2,828,823 4/1958 Mounce 166/187 3,125,163 3/1964 Smith 166/187 3,130,787 4/1964 Mason... 166/187 Primary Examiner-James A. Leppink Attorney-Fetherstonhaugh & Co.

ABSTRACT: A tubular inflatable bag has its lower end secured to a bottom closure cap at the lower end of an air pipe which has a lateral passage for admitting air under pressure into the bag. The upper end of the bag is secured to a top closure cap which is slidable along the pipe as the bag expands during inflation. Upward sliding of the top cap is limited by an abutment provided on the pipe above the bag, the abutment consisting of a housing which contains a valve for controlling airflow through the pipe.

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INVENTOR Peppino BASSANI WWV PATENT A ENTS SEISMIC BOREIIOLE PLUG This invention relates to a fluid pressurized borehole plug adapted for use in the sealing off of seismic boreholes to prevent the flow of subsurface water from such holes.

A borehole plug of this general type is described in US. Pat. No. 3,125,163 issued Mar. 17th, 1964 to \V.G. Smith. In a seismic boring program a large number of boreholes are usually made distributed over a selected area. Most of the boreholes are ultimately closed off by means of a cement plug. However such boreholes often strike water and become in fact artesian wells. The presence of a large flow of water in a borehole causes problems during the sealing operation and to facilitate sealing of such boreholes by means of a cement plug set near the top of the borehole, borehole plugs of the type with which the present invention is concerned were developed. One such bore hole plug, which also includes means for controlling the flow of water in a borehole, is described in the specification of my copending Pat. application No. 709,366 filed Feb. 29, 1968, now U.S. Pat. No. 3,493,045.

According to the present invention I now propose an inflatable borehole plug for sealing off a borehole comprising an inflatable tubular bag of flexible elastic material, first and second end closure caps secured to opposite ends of said bag, a rigid hollow pipe secured to said first end closure cap and extending generally axially of said bag, said pipe extending through an aperture in said second end closure cap, sealing means in said aperture forming a sealing engagement between said pipe and said second end closure cap, said second end closure cap being slidable axially with respect to said pipe, an abutment on said pipe defining a limit to the sliding movement of said second end closure cap away from the first end closure cap, a passage communicating the interior of said pipe to the interior of said bag, and valve means on said pipe operative to seal off the interior of said bag.

Preferably the ends of the tubular bag are secured in peripheral grooves in the end closure caps by means of clamping rings, the end closure caps conveniently being moulded in a suitable plastics material with the lower end of the first end closure cap being smoothly domed to facilitate insertion of the plug in a borehole. The pipe is preferably cylindrical and cooperates with an O-ring seal set in the aperture in the second end'closure cap, the upper end of the pipe carrying a housing for the valve means, which housing also provides an abutment to limit the movement of the second end closure cap away from the first end closure cap.

One embodiment of my invention will now be described by way of example only with reference to the accompanying drawings wherein:

FIG. 1 is an elevation partly in section of an inflatable borehole plug according to this invention shown in its uninflated condition prior to insertion in a borehole; and

FIG. 2 is an elevation of the borehole plug inflated and mounted in sealing engagement in a borehole.

The borehole plug comprises a tubular inflatable bag of flexible elastic material impermeable to gas, the lower end of the bag being secured to a bottom end closure cap 11 and the upper end of the bag being secured to a top end closure cap 12. Each of the end closure caps is moulded in a suitable plastics material and is provided with a peripheral groove 13 to which the corresponding end of the tubular bag 10 is secured by means of a releasable clamping ring 14. The lower end of the bottom end closure cap 11 tapers smoothly to a point 15.

A rigid hollow pipe 16 extends axially with respect to the end closure caps and is in screw-threaded engagement as at 17 with the bottom cap 11. The pipe 16 extends with clearance through an aperture 18 in-the top cap 12 and is sealed thereto by an O-ring seal 19 carried in the aperture, the top cap 12 being movable in an axial direction with respect to the pipe.

It will be seen that the tubular bag 10 together with the end closure caps 11 and 12 form an airtight chamber which communicates with the hollow interior of the pipe 16 through a passage 20 in the wall of the pipe 16 close to the bottom end closure cap 11.

Above the top closure cap 12 the pipe 16 carries a housing 21 within which is mounted a valve (not shown) preferably a check valve which is left in place when the borehole is sealed through which the bag 10 can be inflated. The valve housing 21 is located on the pipe 16 about 5 or 6" above the top closure cap 12 in order to permit longitudinal expansion of the bag 10, thus preventing the tendency of the bag to bulge up around the top closure cap and thus become damaged by puncturing. The housing 21 forms an abutment to limit the upward movement of the top closure cap 12 on the pipe 16, and is adapted to receive a second pipe 22 coaxial with the pipe 16. Thus when the plug is inserted in a borehole air can be pumped through the pipe 22, valve housing 21 and pipe 16 to inflate the bag 10.

The borehole plug is shown in FIG. 1 in condition for insertion in a borehole, i.e., with the bag 10 uninflated, although a small pressure of air may be required in the bag to prevent it collapsing and allowing the top closure cap 12 to move down the pipe 16.

Upon insertion of the plug in a borehole the smooth pointed form of the bottom closure cap 11 facilitates unimpeded progress of the plug downwards in the borehole until it is posi tioned at the desired level. Thereupon air may be pumped into the bag 10 through the second pipe or pipe string 22 to inflate the bag and cause it to expand laterally against the surface of the borehole as shown in FIG. 2, By virtue of the elastic and flexible nature of the material of the bag 10 it accommodates itself readily to irregularities in the surface of the borehole wall and forms a fluid tight seal therewith extending over a substantial axial length of the borehole. As the bag 10 is inflated and expands laterally the top closure cap 12 moves downward on the pipe 16 to accommodate this expansion. Once the bag 10 has been inflated to the required pressure it is maintained in its inflated condition by the valve in the housing 21 which prevents escape of air from the bag.

Thus with the borehole plug positioned in sealing engagement in a borehole as shown in FIG. 2 subsurface water present in the borehole below the plug cannot pass upwards beyond the plug so that the top end of the borehole can without difficulty be sealed off by means of a concrete plug. If it is required to change the position of the borehole plug or to retrieve it from the borehole the valve in the housing 21 can be released in known manner by means inserted through the second pipe or pipe string 22 allowing the bag 10 to deflate to its condition shown in FIG. 1 whereupon it can be moved freely up and down the borehole.

What I claim is:

1. An inflatable borehole plug for sealing off a borehole comprising an inflatable tubular bag of flexible elastic material, first and second end closure caps secured to opposite ends of said bag, a rigid hollow pipe secured to said first end closure cap and extending generally axially of said bag, said pipe extending through an aperture in said second end closure cap, sealing means in said aperture forming a sealing engagement between said pipe and said second end closure cap, said second end closure cap being slidable axially with respect to said pipe, an abutment on said pipe defining a limit to the sliding movement of said second end closure cap away from the first end closure cap, a passage communicating the interior of said pipe to the interior of said bag, and valve means on said pipe operative to seal off the interior of said bag.

2. An inflatable borehole plug according to claim 1 wherein said pipe is cylindrical and said sealing means comprises an O- ring seal carried in said aperture.

3. An inflatable borehole plug according to claim 1 wherein said valve means are provided in a housing carried on the end of said pipe remote from said first end closure cap, said abutment being provided by said housing.

4. An inflatable borehole plug according to claim 3 wherein said housing is adapted to receive and secure a second pipe extending coaxial with said first-mentioned pipe.

5. An inflatable borehole plug according to claim 1 wherein each of said end closure caps has an annular groove formed in the periphery thereof the respective end of said tubular bag overlying said groove and being secured thereto by a clamping ring.

6. An inflatable borehole plug according to claim 1 wherein said first end closure cap tapers smoothly to a point extending in a direction away from said second end closure cap.

7. A fluid-pressurized plug for sealing off a borehole, said plug comprising an inflatable vertically elongated tubular bag which is expansible both radially and longitudinally while being inflated, upper and lower end caps having the respective upper and lower ends of said bag secured thereto, a rigid fluid inlet pipe secured in the lower end cap, said pipe extending axially upwardly through said bag and through an aperture in the upper end cap and projecting upwardly from the upper end cap, the interior of said pipe communicating with the interior of the bag, said upper end cap being slidable along said pipe to permit longitudinal expansion of the bag during inflation, and an abutment provided on the pipe at a point spaced upwardly from the upper end cap when the bag is not inflated, said upper end cap being engageable with said abutment to limit longitudinal expansion of the bag during inflation.

8. The device as defined in claim 7 together with a shut-off valve provided on said pipe and constituting said abutment. 

1. lAn inflatable borehole plug for sealing off a borehole comprising an inflatable tubular bag of flexible elastic material, first and second end closure caps secured to opposite ends of said bag, a rigid hollow pipe secured to said first end closure cap and extending generally axially of said bag, said pipe extending through an aperture in said second end closure cap, sealing means in said aperture forming a sealing engagement between said pipe and said second end closure cap, said second end closure cap being slidable axially with respect to said pipe, an abutment on said pipe defining a limit to the sliding movement of said second end closure cap away from the first end closure cap, a passage communicating the interior of said pipe to the interior of said bag, and valve means on said pipe operative to seal off the interior of said bag.
 2. An inflatable borehole plug according to claim 1 wherein said pipe is cylindrical and said sealing means comprises an O-ring seal carried in said aperture.
 3. An inflatable borehole plug according to claim 1 wherein said valve means are provided in a housing carried on the end of said pipe remote from said first end closure cap, said abutment being provided by said housing.
 4. An inflatable borehole plug according to claim 3 wherein said housing is adapted to receive and secure a second pipe extending coaxial with said first-mentioned pipe.
 5. An inflatable borehole plug according to claim 1 wherein each of said end closure caps has an annular groove formed in the periphery thereof the respective end of said tubular bag overlying said groove and being secured thereto by a clamping ring.
 6. An inflatable borehole plug according to claim 1 wherein said first end closure cap tapers smoothly to a point extending in a direction away from said second end closure cap.
 7. A fluid-pressurized plug for sealing off a borehole, said plug comprising an inflatable vertically elongated tubular bag which is expansible both radially and longitudinally while being inflated, upper and lower end caps having the respective upper and lower ends of said bag secured thereto, a rigid fluid inlet pipe secured in the lower end cap, said pipe extending axially upwardly through said bag and through an aperture in the upper end cap and projecting upwardly from the upper end cap, the interior of said pipe communicating with the interior of the bag, said upper end cap being slidable along said pipe to permit longitudinal expansion of the bag during inflation, and an abutment provided on the pipe at a point spaced upwardly from the upper end cap when the bag is not inflated, said upper end cap being engageable with said abutment to limit longitudinal expansion of the bag during inflation.
 8. The device as defined in claim 7 together with a shut-off valve provided on said pipe and constituting said abutment. 